A pointing device is an input interface that allows a user to input continuous and multi-dimensional data to a computer. The pointing device can facilitate user input of gestures such as pointing, clicking, or dragging. In response to user input, the gestures are translated by a computing device and used to modify a user interface, often by movement of a relative position of a pointer or cursor on the user interface. For example, if a user interacts with the input interface, such as a touchpad, by moving two fingers in a downwards or upwards motion, the user interface may show a scrolling motion on the currently active page. Two commonly used pointing devices are touchpads (also called trackpads) and pointing sticks.
Touchpads are pointing devices that are commonly used for notebook computers. Typically, touchpads have a touch sensor for receiving user input. The touch sensor is configured to enable translation of a position of a user's finger that is detected by the touch sensor to a relative position on a user interface. Touchpads are typically flat (planar) and have a relatively thin form factor. However, touchpads often require a user to repeatedly reposition his or her finger and/or hand when the user desires to move a cursor a long distance across a user interface.
On the other hand, pointing sticks (e.g., Trackpoint® developed by IBM®, etc.) are small joysticks that are often manipulated by a user's finger and are used to control a cursor or other representation on a user interface. Typically, a pointing stick has a vertical shaft and/or spring-mechanisms that “auto-center” the pointing stick after use. Unlike touchpads, pointing sticks do not require repositioning of a user's finger and/or hand on the pointing stick while the user interacts with the pointing stick. While pointing sticks have a small lateral footprint, the depth that the shaft extends below the top of the pointing stick (i.e., effective height) cannot be easily reduced without compromising functionality, such as an auto-centering feature. Accordingly, it is currently impractical to implement pointing sticks with a relatively thin form factor, which may be desirable for use with thin and light notebook computers such as ultrabooks.
Some pointing devices measure optical-flow through a small hole mounted on an upper tactile surface of a pointing device. Such devices are optical sensor-type pointing devices (e.g., Optical TrackPoint® developed by IBM®, etc.). Optical sensor-type pointing devices typically have a small footprint and are suitable for portable devices. However, optical sensor-type pointing devices lack an auto-centering mechanism and accordingly, require repositioning by the user of the device.